The present invention relates to methods, kits and pharmaceuticals compositions useful for diagnosing, delaying onset of, preventing and/or treating osteoporosis and, more particularly, to the identification of an osteoporosis risk haplotype using SNPs present in the CNR2 locus.
Osteoporosis is a systemic skeletal disease resulting in low bone mass and micro-architectural deterioration of bone tissue, causing an increase in bone fragility and susceptibility to fracture. If not prevented or if left untreated, osteoporosis can painlessly result in multiple bone fractures.
Bone tissue, which is mainly composed of collagen and calcium phosphate, is subjected to a constant breakdown and resynthesis (i.e., bone remodeling) in a process mediated by osteoblasts, which produce new bone, and osteoclasts, which destroy the bone. The activities of these cells are regulated by a large number of cytokines and growth factors, many of which have now been identified and cloned.
During childhood and teenage years, the total amount of new bone added is higher than the amount of bone removed and resorbed resulting in a net increase in bone mass. However, beyond the age of about twenty-five to thirty-five, bone resorption slowly begins to exceed bone formation, leading to a net bone loss. Thus, the appearance of osteoporosis and bone fractures is dependent on the peak bone mass accumulated until the age of 25-35 years and the rate of bone mass loss following that peak.
Due to estrogen deficiency following menopause, bone loss is more pronounced in females than in males. In the USA, osteoporosis affects 17% of all postmenopausal women and 30% of women older than 65.
The diagnosis of osteoporosis relies on the measurements of bone density, which is calculated and presented as T-scores. However, the predictability of bone density measurement is relatively low. In addition, more than 75% of women and about 90% of men with a high likelihood of developing osteoporosis are not being tested. Furthermore, in children and adolescents, in whom physical exercise can still affect and increase the peak of bone mass, no densitometric criteria are available (J. Clin. Densitom. 2004, 7: 17-26. The Writing Group for the ISCD Position Development Conference).
Thus, there is a need to develop accurate methods of determining susceptibility towards osteoporosis in both human mates and females at any age.
Osteoporosis-related bone fractures are treated using casts, braces, anchoring devices and other strictly mechanical means. The fractured bone is often replaced by endosseous implants. On the other hand, treatment of the skeletal deterioration associated with post-menopausal osteoporosis is based on the use of bisphosphonates and estrogens, both of which prevent bone loss. However, the use of bisphosphonates may result in serious side effects in the upper gastrointestinal track. Moreover, after several years of treatment, bisphosphonates restrain bone remodeling. This may, in-turn, lead to increased fracture risk. In addition, the use of estrogens may result in increased risks for breast cancer, stroke and cardiovascular diseases (Fontanges E., et al., 2004. Osteoporosis and breast cancer. Joint Bone Spine. 71: 102-10).
Other treatment regimens for osteoporosis include the administration of Teriparatide, a form of the parathyroid hormone, which stimulates new bone formation and significantly increases bone mineral density. However, the use of Teriparatide is often associated with nausea, leg cramps and dizziness. Moreover, the major disadvantage of the use of a parathyroid hormone for preventing osteoporosis is the need of daily injections.
Various other therapeutic approaches of treating bone-related diseases have been suggested. These include the use of osteogenic growth polypeptides for the enhancement of bone formation (U.S. Pat. No. 5,461,034), antiestrogenic oral contraceptive compounds, 3,4-diarylchromans, for the treatment of osteoporosis (U.S. Pat. No. 5,280,040), a recombinant protein containing a bone morphogenic polypeptide (BMP) of the TGF-beta (TGF-β) superfamily of cytokines for enhancing bone growth (U.S. Pat. No. 6,352,973), inhibitors of proteasomal activity and production for inhibiting osteoclastic activity and stimulating bone growth (U.S. Pat. No. 6,462,019), activin and bone morphogenic protein (International patent application No. 92/14481), cell growth factor which induces osteoblast proliferation (European Patent Application No. 499 242), antagonists of parathyroid hormone peptide for the treatment of dysbolism associated with calcium or phosphoric acid, such as osteoporosis (European Patent Application No. 451 867), and fluorides, which increase osteoblast proliferation (Burgener et al. J Bone Min Res (1995) 10:164-171).
Although bone morphogenic proteins (BMPs) are potent stimulators of bone formation in vitro and in vivo, their use as therapeutic agents in enhancing bone healing is limited by the wide-expression of BMP receptors in a large variety of tissues, making BMP's systemic administration essentially unpractical.
On the other hand, the administration of fluorides is often associated with increased bone fragility, presumably due to adverse effects on bone mineralization.
Thus, there is currently a need for developing a safe and useful method and/or composition for preventing and/or treating osteoporosis.
Osteoporosis is a multi-factorial disease, depending on both environmental and genetic factors. Twin studies have shown that genetic factors account for 60-80% of the variance in bone mineral density (BMD).
In order to identify the gene(s) underlying the genetic basis of osteoporosis, numerous linkage analysis studies, case-control association studies and quantitative trait locus (QTL) mapping in animal models were conducted (Reviewed in Yao-Zhong, L., et al., 2003, J. of Endocrinology, 177: 147-196). While linkage analysis studies have implicated a mutation in the interleukin-6 (IL6) gene, several association studies suggested that polymorphisms in the Collagen type 1 α1 (COL1A1) gene and possibly also in the vitamin D receptor (VDR) and calcitonin receptor (CTR) genes, are associated with osteoporosis. However, other association studies suggested a relationship between susceptibility to osteoporosis and genetic variations in the 5′-flanking region of the RIL gene encoding a PDZ-LIM domain protein (Omasu et al. 2003, Association of genetic variation of the RIL gene, encoding a PDZ-LIM domain protein and localized in 5q31.1, with low bone mineral density in adult Japanese women. J. Hum. Genet. 48: 342-345) or with exon 10 of the low-density-lipoprotein-receptor-related receptor-related protein 5 (LRP5) gene (Mizuguchi et al. 2004. LRP5, low-density-lipoprotein-receptor-related protein 5, is a determinant for bone mineral density. J. Hum. Genet. 49: 80-86).
While reducing the present invention to practice, the present inventors have uncovered that mice lacking the CB2 receptor gene (CNR2) exhibit low bone mass and high bone turnover. In addition, the present inventors have uncovered that SNPs in the CNR2 locus are highly associated with osteoporosis and that such SNPs can be used in determining predisposition to osteoporosis.